How to build different scenarios in the Compositor
I see a couple of options:


1 Using a new scene.

Without having to create new files you can use a new scene with linked objects. Changes in the compositor for one scene will not affect the compositor options for other scenes:




2. Using a a Switch and/or Split viewer node 

The switch node allows you to re-route the node flow, so you can compare different inputs:





A split viewer node creates a viewer that allows you to compare both inputs simultaneously, by splitting the window horizontally or vertically.